C ; The are most active at temperatures about 53 degrees
        
             
        
        
        
<span>By discovering height and length of a bone forensic experts are able </span>to tell the person’s weight, the racial group to which
the person belongs. With other characteristics of the bones, the experts can discover age,  if the person was a male or female and what traumas suffered before.
        
                    
             
        
        
        
They find shells that other crabs have left behind and use them
        
             
        
        
        
I believe the correct answer would be <span>variation. The definition of variation in biology means,</span><span> any difference
between cells, individual organisms, or groups of organisms of any
species caused either by genetic differences or by the effect of environmental factors on the expression of the genetic potentials. So i think that organisms can also be classified as variation. Hope this helped. ♥ ☺
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Answer: It helps in the removal of abnormal heart rhythm 
Explanation: 
The AHA's chain or survival includes many steps in it. This is required to save the life of a person in emergency conditions.
One of the main step in AHA's chain of survival includes Rapid defibrillation which is given to a person after CPR.
This condition eliminated the abnormal cardiac rhythm. Electric shocks are given by the medical team so as to treat the emergency conditions like heart attack, cardiac arrest, et cetera.